1. Field of the Invention
The present invention relates generally to compression spray applicators for coating fluids, and more particularly to such a spray applicator for spraying viscous fluids, such as plaster or other texturizing material, onto a wall, ceiling or the like.
2. Background Art
There are in the prior art spray applicators where there is a chamber which contains a viscous fluid, such as plaster, with a forward fluid discharge nozzle through which the plaster is sprayed. There is a source of pressurized air (e.g., a manually operated cylinder and piston air pump, or possibly an air pressure structure which can be attached to a powered air compressor) from which air is discharged through an air nozzle which is axially aligned with, and positioned rearwardly of, the fluid discharge nozzle. The plaster or other material to be discharged moves into alignment with fluid discharge nozzle, and an air jet from the air nozzle propels the plaster or other fluid through the fluid nozzle in a spray pattern.
One such spray applicator is shown in U.S. Pat. No. 4,411,387 (Stern et al.), issued Oct. 25, 1983 and entitled "Manually Operated Spray Applicator". There is shown a spray applicator where there is a cylinder defining an air chamber, with a manually operated piston being positioned in the chamber in a manner that reciprocating motion of the piston causes air to pass through an air nozzle during the forward stroke of the piston. When the air in the air chamber becomes pressurized, it acts on a nozzle positioning plate to move the air nozzle rearwardly away from the fluid nozzle to permit the plaster or other fluid to pass into alignment with the fluid discharge nozzle so that this plaster or other fluid is discharged in a spray pattern. One of the problems toward which this patent is particularly directed is to stop the "dribbling" of the plaster or other material from the fluid discharge nozzle at the end of the piston stroke when the air pressure in the air chamber is dropping back to atmospheric pressure. To alleviate this, the apparatus is arranged so that just before the completion of the compression stroke of the piston, a pressure relief passageway is opened to permit a spring acting on the nozzle member to move the nozzle member forwardly to a closed position. On a subsequent stroke of the piston, the forward motion of the piston again pressurizes the air chamber to act through a passageway to act on the positioning plate to move the air nozzle rearwardly to its open position and again permit the discharge of the plaster or other material as a spray.
While the spray applicator described in U.S. Pat. No. 4,411,387 is certainly a practical and commercially viable design, there is perceived a need to provide a spray applicator of a simplified design which can be manufactured economically, yet which is reasonably effective in accomplishing a proper spray application of the plaster or other material. For example, such a simplified spray applicator would be desirable in a situation where a person needs the applicator for only limited use, such as spraying the plaster on a small area of a repair. For such an application, it may not be necessary to have all of the operating refinements of a more sophisticated spray applicator, but yet have the basic operating characteristics which provide overall effective operation.
It is toward this problem which the present invention is directed.